fix(module): allow client side push before init

[1ed]

With this patch we can push client side events before the container loaded event:

export default function gtmPlugin({ app, $gtm, $storage }) {
  if (app.$config.GTM_ID) {
    $gtm.push({ data: $storage.get('key') }); // this data only available in localstorage 
    $gtm.init(app.$config.GTM_ID);
  }
}

Kind of a follow up on #51

This is the diff for the compiled script:

if (!window._gtm_init) {
  window._gtm_init = 1;
  (function (w, n, d, m, e, p) {
    w[d] = (w[d] == 1 || n[d] == 'yes' || n[d] == 1 || n[m] == 1 || (w[e] && w[e].p && e[e][p]())) ? 1 : 0
  })(window, 'navigator', 'doNotTrack', 'msDoNotTrack', 'external', 'msTrackingProtectionEnabled');
  (function (w, d, s, l, x, y) {
-   w[l] = w[l] || [];
-   w[l].push({'gtm.start': new Date().getTime(), event: 'gtm.js'});
    w[x] = {};
    w._gtm_inject = function (i) {
      if (w.doNotTrack || w[x][i]) return;
      w[x][i] = 1;
+     w[l] = w[l] || [];
+     w[l].push({'gtm.start': new Date().getTime(), event: 'gtm.js'});
      var f = d.getElementsByTagName(s)[0], j = d.createElement(s);
      j.async = true;
      j.src = 'https://www.googletagmanager.com/gtm.js?id=' + i;
      f.parentNode.insertBefore(j, f);
    }
  })(window, document, 'script', 'dataLayer', '_gtm_ids', '_gtm_inject')
}